Okay, so you have on the motherboard all the main voltages, further no activity, only the two network leds are on.

What you can do is to check the C115 cap voltage for 3.3v.
This is the fourth cap from the four big caps, near the jtag connector (14 pins).
Is this present, than you can try to replace these cap.
Because, if this cap is bad, than you may get this symptom.

Further you can try to see if there is any activity by using a terminal program as Hyperterminal or Putty.
Use a 0 modem rs232 cable and connect it to the service port.
Use the terminal settings,

Bits per second = 115200
Data bits = 8
Parity = None
Stop bits = 1
Flow control = Xon / Xoff

If you have replaced this cap, or often better all the four big caps and you have no results, or any output data from the serial port.

Than it could be a u22 issue (if it's the seven pins version) otherwise it is most likely a cpu, or memory issue.